Banks buying back risky mortgages

JPMorgan Chase is buying $6b worth of risky mortgages into its own investment portfolio. How could banks be involved in risky products? Or why would banks be allowed to take on such risk?

Let's hope this kind of practices stay in the US and our local banks are not allowed to be too adventurous again. Banks are the bedrock of the whole financial system and should not be running around like koyok